Yendon – Process Flow Sheet

The process of refining kaolin into HPA has 2 distinct stages:

1.) Beneficiation of the mined ore

This stage is undertaken at the Yendon mine site and consists of a simple physical separation based on particle size. The PFS studies have determined that using a 63µm cut off, the alumina content is significantly upgraded while also removing a significant proportion of impurities, mainly silica.

2.) Concentrate refining to produce HPA

This process has been the main focus of the PFS studies. The basic hydrometallurgical process was published in a 1946 paper in the Journal of Research of the National Bureau of Standards in the US. As each kaolin deposit has its own mineralogy and physical characteristics, this process has been modified specifically to suit the Yendon concentrate.The process consists of leaching in HCl, precipitation of Al2O3 into crystal form and then repeating the process several more times. There are also some intermediate purification steps that were developed by Pure Alumina to optimise the Al2O3 recovery from the Yendon ore.The final step is to roast the purified crystals at 1,100oC to remove the Cl and oxidise the final product.